Nuclear medicine is a unique medical specialty wherein radiation is used to acquire images which show the function and anatomy of organs, bones or tissues of the body. Radiopharmaceuticals are introduced into the body, either by injection or ingestion, and are attracted to specific organs, bones or tissues of interest. Such radiopharmaceuticals produce gamma photon emissions which emanate from the body and are captured by scintillation crystals with which the photons interact to produce flashes of light or events. In SPECT, events are detected by one or more collimated gamma photon detectors, also referred to as gamma cameras, which are typically rotated about a patient's body. Using the experimental data that is collected, three-dimensional images of the organs of the body, which have been taken up the radiopharmaceuticals, e.g. the heart, can be constructed.
While SPECT is a powerful tool in the clinician's toolbox, it suffers from at least one drawback—SPECT imaging can be time consuming when compared with other types of imaging procedures. For example, whereas CT scanning procedures can take as little as a minute to complete, SPECT procedures can take more than fifteen minutes to complete. This is problematic because it can be difficult for a patient to remain still for such time periods, which can affect image quality. Similarly, some patients may be unwilling to undergo scanning procedures that take such long periods of time.
The amount of time that it takes to scan a patient using SPECT can be attributed to a number of factors. Most significantly, however, is the fact that SPECT detectors include collimating devices that only allow gamma photons traveling along precise trajectories to interact with the detectors. As a result, it can take time for a sufficient number of gamma photons to interact with the detectors to produce an image. Other factors that can affect SPECT scanning time include, but are not limited to, the distance between an object and a detector, the amount of tissue between an object and a detector, and angle of orientation of the SPECT detectors with respect to the object being studied. For example, many SPECT detectors are oriented at −45° starting angles and travel along elliptical trajectories centered about a patient's body. However, areas of interest, such as the human heart, are centrally located within the body. As a result, the distances, angles of orientation, and trajectory of the SPECT detectors are not optimized, or geometrically efficient, for performing such scans. Consequently, unnecessary time is expended when scanning such objects using these types of systems.
What is needed then is a method for optimizing a starting angle of a SPECT detector to maximize the geometrical efficiency of the detectors along a trajectory.